1. Field of the Invention
The present invention relates to a zoom lens structure, and more particularly to utilize a screw bolt for fastening the front and the rear track lens barrels and allow the front and rear lens groups to be effectively shifted in association with only a single driving source through interaction of the tracks and guiding grooves.
2. Description of the Prior Art
Referring to FIG. 1 for a conventional zoom lens structure, the zoom lens structure comprises at least a first lens group 11, a second lens group 12, a fastening ring 13, a cylindrical cam barrel 14, an external barrel 15 and a driving gear wheel 16, wherein the first lens group 11 has a positioning slice 111 and a pulley 112; and the second lens group 12 has a positioning groove 121 and the pulley 112, and the fastening ring 13 has a positioning slab 131 and a protrusion 132; the cyclindrical cam barrel 14 has multiple male threads 141, gear tooth 142 and curve grooves 143; the external barrel 15 has straight line grooves 151, multiple female threads 152 and a long slot 153. From this diagram, the positioning slice 111 of the first lens group 11 is disposed on the positioning groove 121 of the second lens group 12, and the positioning slab 131 of the fastening ring 13 is also disposed to the positioning groove 121 of the second lens group 12; and the first lens group 11, the second lens group 12 and the fastening ring 13 may not produce relative displacement through the positioning slice 111, the positioning slab 131 and the positioning groove 121; and the first lens group 11 and the second lens group 12 are disposed inside the cylindrical cam barrel 14 and the pulley 112 of the first lens group 11 and the pulley 112 of the second lens group 12 are disposed to the curve groove 143. The cylindrical cam barrel 14 then is disposed inside the external barrel 15 so that the multiple male threads 141 of the cylindrical cam barrel 14 and the multiple female threads 152 of the external barrel 15 may contact with each other, and the protrusion 132 of the fastening ring 13 will also be disposed to the straight line groove 151 of the external barrel 15. The cylindrical cam barrel 14 then is driven for rotation through the driving gear wheel 16 disposed to the long slot 153 of the external barrel 15, and because of the interaction of the multiple female threads 152 of the external barrel and the multiple male threads 141 of the cylindrical cam barrel 14, the cylindrical cam barrel 14 can be stretched out from the external barrel 15 so that the first lens group 11 and the second lens group 12 then are further stretched out from the cylindrical cam barrel 14 to achieve the zooming effect.
However, the first lens group 11 and the second lens group 12 can only shift within a narrow range provided by the zoom lens structure, thus resulting in highly restricting the zooming effect. To enhance the zooming effect, researchers seek to lengthen the two lens groups to provide sufficient zooming distance. But this requires two driving sources for control, and the entire volume is increased.
To satisfy the requirement for better zooming effect through one driving source, the inventor of the present invention, with years of research and practical experience of the industry, has presented this zoom lens structure.